Childhood lead exposure is associated with lower cognitive functioning at older ages

Abstract

The Flint, Michigan water crisis renewed concern about lead toxicity in drinking water. While lead in drinking water has been shown to negatively affect cognition among children, much less is known about its long-term consequences for late-life cognition. Using a nationally representative sample of U.S. older adults linked to historical administrative data from 1940, we find that older adults who lived as children in cities with lead pipes and acidic or alkaline water-the conditions required for lead to leach into drinking water-had worse cognitive functioning but not steeper cognitive decline. About a quarter of the association between lead and late-life cognition was accounted for by educational attainment. Within the next 10 years, American children exposed to high levels of lead during the 1970s will enter older ages. Our evidence highlights the need for stronger actions to identify interventions to mitigate long-term damage among people at high risk.

Fig. 1.. Conceptual framework of life course processes through which childhood lead exposure shapes cognitive function.

Incorporating the life course perspective, we posit that childhood lead exposure may affect cognitive functioning through direct (solid line) and indirect (dashed line) pathways. The italicized font indicates demographic and childhood covariates adjusted for in all models that include age, sex, race, childhood SES, childhood health, and place of birth.

Fig. 2.. Location of cities that had lead pipes and acidic/alkaline water in 1940, the conditions required for lead to leach into municipal water.

Cities with lead pipes and acidic/alkaline water are marked on the map with red solid circles, and those with lead pipes and neutral water are marked on the map with red open circles. Cities using nonlead pipes regardless of water pH are marked on the map with gray open circles. Water pH level less than 6.5 or greater than 8.5 is considered acidic and alkaline water, respectively. Data source: The Manual of American Water-Works (30) and the U.S. Geological Survey (31).

Fig. 3.. The chemistry of water and lead.

The lead concentration varies by water chemistry. For people whose municipal water has pH values less than 6.5 or greater than 8.5, we would expect lower cognitive functioning as lead levels in their bodies would have increased as lead from water lines leaches as the result of alkaline or acidic water chemistry. However, for people whose municipal water has a pH level between 6.5 and 8.5, lead municipal water pipes are less problematic because the lead is not readily leached into the water. Adapted from (12) with permission from Elsevier.

Fig. 4.. Trajectories of cognitive functioning by childhood lead exposure.

Trajectories are calculated using estimates from model 1 in Table 2, HRS, 1998 to 2016 (n = 7432 person-wave observations).